Core taking apparatus



Aug. 28, 1956 J. R. YANCEY ETAM.v 2,760,758

CORE TAKING APPARATUS Filed March '7. 1952 3 Sheets-Sheet l 28 2 2; gwoa/wtofv JU//A/ /ff 74A/ffy JASEPH WWYL 0f? M4/naw l ATTOR N EYS y y i ,v L... a 0 QV i 7m M) M W 2 y, y l Livi i; A f y0..` u m A M A o lv 0 Q x u I IAA 4 4, w m M /7 mf@ f ,a 2 m @y n M 2 W Aug. 28, 1956 J, R, YANCEY ETAL 2,760,758

CORE TAKING APPARATUS Filed March 7, 1952 :s sheets-sheet 2 ATTORNEYS Aug. 28, 1956 J. R. YANCEY ETAL 2,760,758

CORE TAKING APPARATUS Filed March '7, 1952 3 Sheets-Sheet 3 gwen/VTM United States Patent "CORE TAKING APPARATUS .'John'R.=Yancey 'and AJoseph W. Taylor, Houston, '"Tex., '.as`signors,itby.mesne assignments, to lU. S. Industries, luc.; al corporation of Delaware LApplication'Marh 7, 1952,..SerialNo. 275,268

i8 Claims. (Cl.l Z55-572) Thisin-vention pertains toapparatus for obtainingcores .or samples of formationfr-omzthe bottom of a welk. parvticlarlyan oilwell, when `drilling .the .same forsubsequent inspection and analysis off-.thez-sample. More. particularly, `"this" invention relates to wireline coring equipment-where- Ain' a core barrel isinsertableinand .removable from a core Vdrill .through ,the operating string .of pipe. In .such instances "the corel barrel .is retrievedthrough the vdrill string by a'iishing or retrieving `tool attached on the endof a wire iline, whereby the retrievable `core barrelsof this typehave r'become knownas wireline core. barrels.

Wirel line type coring equipmentis known intheart, but previous .apparat-uso-f'xthis vnaturehas necessitated. a reduc- 'tionf belo-w normaldrilling rates, of vboith R. P.. M. .ofthe coredril'l` and pressure of.the..drill Huid which isl pumped down through.. the .operatingstring for. dischargefrom the vd'r'illat the .bottom-ofthe well. The .drill iluid `returnsupwardly to themouthof :the well through. the `space vbetween nfthefoperating. string.l oipipe andthe walls of: `the well-.to -provide a .circulation whichy carries 'away the cuttingsand .also `cools .the ..bit. Additionally, `such .iiuid usually'. is g jetted fromthe drillfatchigh velocityagainstthe. `face of '.ftheformation being cut in. order to aid. the .actual cutting :.-.operation.

v.'Fhenecessityof .reduced R..^P..M.s.and drill iluidpres- Msureswheneoring,y below thosenormallyemployed in ordi- :.-.nary-drilling,.is.caused bythe fact .that .heretofore an effective seal has not beenlobtainedbetween:thecorelbarrel ..and.1the.fcore drillto prevent: :escape vof` .drill liui dtthrough .'Iheentralwcorc receivingspassageway. inV the rcorevfdrill. Previous sea-ls..of.:this nature leaked at ordinarydrillwuid pressures-whicharequitehigh, :so that the combinationof A.high,.pressure :and the -extreme1abrasivecharacteristics-of `:drill .fluidrapidly wore` away the :p arts forming. .the-` seal. LEVemiLmetaI-to-metal.seals wereemployed, :suchtmetal 'lwouldbe abraded. away.by.any.leaksttherebetween,.there- ...lJy-rapidly increasingwthe size of therleakL .and .ultimately `destroying.the equipmentina relatively shorttime. :Ad- .Aditionallypbecausecf ftheidneectiveness .of previous seals, 4eafpartwof .-thedrill .duid would `beodiverted. through. thereonwtral.` core-receivingpassageway with :consequentreduction v...in..available .jetting ..pressure. Further-,..previousiseals .be-

ucause offtheirustructural. .arrangement fandalso. because of developed leaks, would permit formation. being cut.-to..-be wome.: lodged betweenwthecore. barrel-andthe core. drill with resultant L.sticking cfs-the ybarrel within the drill. .Uponthe occurence .of this-latter eventall the advantages tof=wire line curing-are` lost because whena core y.barrel Vsticks itcanznot. be retrieved by a Wire line andthe.. entire 7drill-.string .must- .then bel pulled-.Ito .remove the corerbarrel ornanalysis fof. thefsarnple therein.

Another objection to. some existing types .of-.wireline .-coiringtequipment .is -the-fact that non-metallic packing lf'meansfwhen.- employed .tol form. the seal between. the. .core barrel .and ...the-core `drill,.isl mounted on the..core barrel. tiHence, when: lowering the barrelthrough the :drill string .or -;-:retrieving..the same therethrough, the, packing is. so damaged by contact with various abutments or projections,

Patented Aug. 2.8 1956 ICC ing equipment presently in use is yop-erate'dcat reduced .diill uid pressures to avoid leaking of thess-ame past the 'barrel into Ithe core-receivingpassageway. .lSuchfpressurc reductions necessitated `correspond-ing .reductions lin `R.P.M.s of Ythedrillfso `that present-wireline. curing-operation-s are carried onat rates .of penetrationconsiderably less .thanthat binomial drilling operations. .Sincedrilling equipmentfand the labor, necessary tooperatethesame are quite expensive, reduced rates of penetration'increase drilling costs materially. `This"isespecially ytrue of exploratory wells.

Accordingly, itis an objectfofthis invention yto...p1' 0vide Lwire :line coring equipment-that is ,effective -for its: intended .purpose and which may be operatedat. drill iiuid pressures .and drill. R.P.M-.s asV high as thoseemployed .for ordinary drilling, with consequent high penetration rates.

it is `ano-ther. object ofwthisinven'tion `to provide-.an effective seal lbetween a wireline core barrel and a coredrill :which will notleak athighedrill iiuid pressuresandwill .not permit `formation. t-o becomelodgedbetween"the core barrel. and the `drill lto thereby stick the barrel in the drill 1 and .preventwire line retrieving of vthe .-former.

It is still. another object. of this. invention to provide-.wire

.. linecoring equipment having a seal betweennthecore barrel .and .the .core Ydrill lthat is effective athigh drill .fluid pressures and inrwhich .the core-'barrel may: be replaced "by a wireline plug. bit for. ordinary drilling.

Itis still .another object of this invention to provide-wire line. coring .apparatus with. an .improved plug bit.

Vit is still another objectfof this invention to providefwire line coringapparatu-s oftimproved .design which reduces turbulence-ofv the highvelocity drill iluidywithintheapparatus to thereby. decrease the abrasive eiect of-.|the .drill uid. on the apparatus.

.It is still.- another objectl of .this invention; toA provide wire line-v coringiequipment. withran vimproved seal between the drill -andi'ithe-:core barrel, which seal is xed within `anti .to I the core. drill -to 1 ,thereby be undamaged "by .travel of the co-re`barrel'thr1ough. the drill stri-ng.

- It .is a furtherl object of' thisinvention' :tof provide:. im-

fprovedr` wire. liney core z taking r equipmentrfwhich :is irelatively t simple in f design .and, therefore, economicalfto .i manufacture.

.Other v objectsv and advantages. of .the :invention-will be apparent from the-.following description land. accompany- .ing drawings, in which:

#Figure4 l., is avertical-sectional view of wire ylinecoring f equipment .embodying .this 4invention s. and showing, .the

equipment in operative position at the bottom of a bore hole.

\'Figure '.2' is an. enlarged-.fragmentary yView` of the ,drill bit-and. the lower end-offthe core-barrel`showny infl-"gig- .-urev 1.

Figure 3-is'a-view. corresponding to Figure 2, but showing the "core barrel yreplaced'b'y'aplug bit embodying this invention.

.Figure-4 is: a viewfof thefforward ory lower nendfof the equipments shown in. Figure 2.

`Figure 5,-is-a'viewof the forward or lower-.end of .the

.. on .line 7-7. of Figure .2.

Referring -now to the drawings, .there is. shown inl-ligure ,1. a hollow core'drill1-0 which is .connetableby a sub 12 tothe usual .operating string of pipe'(not shown)'for rotation thereby andr for reception ofV drill fluid therefrom.

The core drill consists of the usual drill collar 14 of any desired practical length and having a tubular bit 16 threaded onto the lower end thereof. This bit 1.6 preferably is manufactured in two parts 18 and 20 which are subsequently welded together as at 22 to facilitate the fabrication of the forward or lower part of the bit. The bit 16 is provided with a plurality of circumferentially spaced large cutting teeth 24 having both radial and axial cutting edges. In the forward end of the bit 16 there is provided a central core-receiving passageway 26, preferably surrounded by a plurality of cutting teeth 28 of lesser radial dimension than the large teeth 24 and which extend axially forwardly of the large teeth to cut in advance thereof. The bit 16 is interiorly enlarged adjacent the rearward end of the core-receiving passageway 26 to form a rearwardly facing frnstc-eonical surface that provides an inside seat 30.

A plurality of lateral enlargements 32 in the bit 16, two as shown in the drawings, provide forwardly facing wall portions 34, each having a tapped opening 36 therein. Threaded into each port 36 is an orifice fitting 38 provided with a wear-resistant insert 40 to avoid cutting away or undue abrasion of the fitting by the high velocity jet of drill fluid emerging therethrough. Preferably, an O-ring 42 is disposed in a circumferential groove between each fitting 38 and the walls of each port 36 to provide a fluidtight seal. It will be noted that in operation of the drill 10, drill fluid is jetted at high velocity against the bottom of the bore hole 44 to both aid the cutting action of the bit 16 and to wash away the cuttings. Additionally, as is well known in the art, drill fluid serves to cool the bit.

Disposed within the core drill 10 is a wire line core barrel assembly 46 of a substantially uniform outer diameter less than the inne-r diameter of the drill 10 (and of the sub 12) to provide a passageway 48 for drill fluid therebetween. The assembly 46 has a tubular core-receiving barrel 50, to the forward end of which a core catcher head 52 is connected by a barrel sub 54. The forward end of the core catcher head 52 is bevelled to provide a frusto-conical surface 56 substantially complementary to the inside seat 30 for seating engagement thereon. Rotatably mounted within the core catcher head 52 is a core catcher assembly 58 having the usual spring ngers 60 which grip the cylindrical formation rising into the barrel assembly 46 through the core-receiving passageway 26 during a coring operation. When the core barrel assembly 46 is withdrawn from the drill 10 through the sub 12 and upwardly through the drill string, as will be explained later, the spring fingers 60 break off the formation and retain the same within the barrel assembly to provide a core for analysis at the surface of the well. It will be noted that the inner diameter of the entrance end of the core catcher head 52 is no smaller than that of the core-receiving passageway 26 of the bit 16 so that the entering core, properly sized by the bit, is undisturbed in its passage into the core catcher head.

The upper end of the barrel 50 has the plug-like end 62 of a latch body 64 threaded thereinto. This end 62 of the latch body is provided with an axial recess 66 having lateral ports 68 at its inner end in communication with the uid passageway 48 between the core barrel assembly 46 and the inner walls of the drill collar 14. The recess 66 is counterbored to provide a shoulder against which seats a valve seat insert 70 that is held in place against the shoulder by a nipple 72 threaded into the recess. A ball valve 74 is disposed within the inner portion of the recess 66 for seating engagement with the valve seat 70, so that drill fluid is prevented from entering the core barrel assembly 46 via the ports 68, but air or other fluid trapped within the core barrel assembly by formation rising upwardly therein may escape through the recess and out of the lateral ports in the latch body 64 when the pressure of such trapped uid becomes suicient to raise the ball valve 74 from its seat 70.

CII

The upper portion of the latch body 64 is tubular and provided with a longitudinal slot 76 in the side wall thereof. A latch 78 is pivotally secured within the upper tubular portion of the latch body 64 for movement through the slot 76 radially of the core barrel assembly 46 by means of a hinge pin 80 extending transversely through the latch body at the lower end of the tubular portion thereof. Thus, the latch 78 may be moved radially outwardly into the position thereof shown in Figure l, but may be moved inwardly within the confines of the latch body 64 by means later described. A latch spring 82 is interposed between the free end of the latch 78 and an opposed side wall portion of the latch body 64 opposite the slot '76, so that the latch is constantly urged to move radially outwardly into the position shown in Figure l.

A cylindrical latch spear 84 is mounted for reciprocation within the tubular portion of the latch body 64 and is provided with lower bifurcated portions 86 straddling the latch 78. The latch 78 has a longitudinal slot 88 therein provided with an inclined side edge 90. A pin 92 extends through the slot 88 in the latch 78 and has its ends secured to the bifurcations 86 of the latch spear 84. This pin 92 engages against the inclined side edge of the slot in the latch, so that upon upward or rearward movement of the latch spear 84 the latch is cammed back into the confines of, or Within the peripheral outline of, the latch body 64. The upper end of the spear 84 is provided with a stern which terminates in an enlarged head 94 for engagement by a fishing or retrieving tool (not shown). Preferably the head 94 has a bevelled outer end 96 for reasons later described.

Suspended by legs 98 depending from a supporting ring 100 threaded into the lower end of the sub 12 is a driving collar 102 which relatively loosely embraces the outer periphery of the core barrel assembly 46. When the latch 78 is in the position shown in Figure l, it will be seen that the free end of the latch is disposed directly beneath the undersurface of the driving collar 102, so that the entire core barrel assembly 46 is locked in position on the inside seat 30 in the drill 10. Depending from the undersurface of the drill collar 102 is a tooth 104 for engagement against the side surface of the latch 78 upon rotation of the core drill 10 by the operating string, so that the core barrel assembly 46 rotates with the drill during the coring operation.

It will be noted that the upper edge of the driving collar 102 is oppositely bevelled, the inner bevel 106 serving as a means for centering and guiding the core barrel assembly 46 in its downward movement through the collar into position within the bit 16, and the outer bevel 108 serving as an aid in streamlining the flow of drill fluid downwardly past the collar during the coring operation. The elimination of turbulence is essential in order to attain the high ilow rates necessary for effective jet action. In this latter connection it is also to be noted that the bevelled formation 96 of the spear head 94 also aids in streamlining the flow of drill fluid downwardly past the spear head. It also is pointed out that the drill collar 14 is interiorly enlarged adjacent the driving collar 102 to prevent choking of the downward flow of drill fluid at this point.

Rearwardly of the inside seat 30 within the bit 16 there is provided a smooth-walled cylindrical section 110 of only slightly larger diameter than that of the core barrel assembly 46. Rearwardly of this section 110 the bit 16 is interiorly enlarged for reception of a tubular seal assembly 112 adapted to embrace the core barrel assembly 46. The seal assembly 112 has a tubular housing 114 threadedly connected, at its lower or forward end, to the bit 16. Preferably, an O-ring seal 116 is disposed in an annular groove between the seal housing 114 and the bit 16 just rearwardly of the threads connecting the same to provide a fluid-tight seal between the housing and the bit. The seal housing 114 is interiorly enlarged above its `threadedlower endto provide an'upwardly"facingfsllder 11S .against lwhich seats a' seal' ring'12`0 having *an inner axially-extending circumferential flange'12'2. `^Re celved within the -housing`114 and having one"ofits"'e'nds yintertting with the seal ring" 120 is a packingjsleeve 124 f 'of resilient'heat-resistant material which snugly Yembraces the outer surface of the `corebarrel'assembly "46. fAlthough this sleeve 124 may be formedof any appropriate vpacking material'having the aforementioned 'desired characteristics, various types of synthetic rubber have been found to besuitable for this purpose. The sleeve 4124 lis clamped within the seal`housing114bymeans of a retaining nut 126 threadedinto `the upperendfof the seal housing 114 and'having'an inner axially-extending circumferential flange 128 at the lower end thereof"interiitting with a complementary upper end of the 'sleeve 124. The upper edge of the nut 126'is interiorly b'evelled to guide the core barrel assembly 46 into the seal: assem- -In useof the apparatus, the core barrel assembly'f46 'is lowered v'or pumped down through the drill pipe until it seats in-operating position against the inside"seat"3 'in the bit 16. As the core barrel assembly 46' enters the sleeve 124, the resulting choking effect on vfluid ow (which theretofore Vpartially flowed outwardly through the core receiving `passageway.26) effects a pressure 'riseof the drill fluid that forces the barrel assembly firmly against the inside seat of the bit and also forces fluid through the jet orifice iittings'38 at high velocity. Thereupon, the coring operation commencesby rotation of the Idrill string and the resultant drilling '-action Wof1the1'bit, fwhich, in turn, permits the drill string, together With' the core drill-10, to move downwardly. The bit.16,f.in"mov- During this coring operation theleffectivenessfofthe sleeve 124 in forming-a tight fluid seal between the core barrel assembly and the bit permits rotation ofthe bitV at normal drilling speeds and also permits normal drilling pressures to be employed. Additionally, because all of the drilling fluid escapes through the jet orifices 38 without a portion thereof being diverted past the inside seat 30 and through the core-receiving passageway 26, the desired high velocity fluid jets are attained. Because uid pressure during the coring operation is greater within the core drill 10 than in the bore hole 44, the fluid pressure passing between the retaining nut 126 and the core barrel assembly 46 acts on the upper end edge of the resilient sleeve 124 to compress the latter into tight sealing engagement with the outer periphery of the core barrel assembly.

When the coring operation has been completed, i. e. the drill 10 has moved downwardly a distance sufficient to obtain a core of the desired length for sampling purposes, the pumps (not shown) at the surface of the we ll are stopped so that the fluid pressures within the core drill 10 and in the bore hole 44 may equalize through the jet orifices 38. Thereupon the drill string is raised slightly so that the core catcher assembly 58 breaks off the core. A retrieving tool (not shown) then is lowered by a wire line through the drill string into engagement with the spear head 94. A subsequent upward movement of the tool first serves to retract the latch 78 by the camming action of the latch pin 92 against the inclined side edge 90 of the slot in the latch, and then pulls the entire core barrel assembly 46 upwardly through the drill string to the surface where the core may be removed from the core barrel assembly for inspection and analysis.

After the coring operation has been thus accomplished and itis desired to resume normal drilling, a separate plug Abit assembly 130 of the same uniform diameter as the Acore-barrel assembly 46 is either pumped or lowered by awire line through the operating string to replace the "core barrel i assembly. This ylsepa'rate* plugi-'bit assembly 130 is shown in Figure' 3, -and'fsincefthefupper Vjportions thereof including a t"ball 'check l'valveya Ilatch assembly,' and a -'spear head Easserribly nare identical fv'vith 5 those 'ofthe c'ore barrel assembly 546,'a-deta'iled 1description of thesepartsis unnecessary. "The-lower* portions of the separate bit assembly `130`consist of a'lplugibarrel Ismaller teeth v28 'ofthe main-bit y-'1'6, so that Aduringfthe :normal drilling operation the separate`v bit "13'4-actsiso'mewhat like a pilot,in`that it 'drillsf'a small centrall-holein vadvance of the action of-the'mainbit.

It will be noted that-.the'plug'bit' 134 -is 'imperforate and that the packing sleeve Ai12-4f makesla tightfseal therevagainst so that lthe sameeifectivenessof jetaction'isobtained by the drill' 10' withthe separatefbit-assernbly in place as Whenfthecoreibarr'el assembly'isfinf use. lA large( pressure differential between the interior ofthe core drill`10-'and the bore hole-"44 also -serves "to main- 'tain the separate bit assembly"1"30firmly seated against the 'inside Aseat '3021s well'asincreasing the effectiveness of ythe sealing action of thefpackingsleeve' 124. A"Even though the separate*bit'asse'mblyy I30"(andalso the core :barrel assembly 46) maybetunseatedslightly"during the drilling operation aridibits "of iforrnationfconsequeritly tend to Work their.' way upwardlypast the'inside' seat-30,

"sincethere is'no"fluid'movementupwafdly toward the sealbetween the`sleeve'1`24and the exteriorofthe'sepa- "rate 'bit' assembly (or off'the'fcore" barrel assembly), f no diiiiculty is encountered in "such" bi-ts" of 'formation' tending toA damage the sleeve.

:Whenever normal'drilling is to4 be interrupted for "fthe purpose of'ta'king a core,`the pumps Vare again shutdown, `the"drill string' raised slightly, and Vthefseparatebitfas- 1.4()

se`rr`1blyf13tl-l lpulled upwardly through' the drill string" 'by means" of a retrievingtool on fthe* end! of a wire line, in

"eXactly' thev 'same' manner as i the withdrawal oft-he core VVbarrel assembly. '-'Thereupom *the coreiba'rrel Yassembly 46 is either pumped down or lowered through the operating string, as before, the pumps are started again, and the drill string is rotated for the core taking operation.

lt will thus be seen that the objects of this invention have been fully and effectively accomplished. It will be realized, however, that Various changes may be made in the specific example illustrated and described for the purpose of disclosing the invention without departing from the principles thereof. Therefore, this invention includes all modifications which are encompassed by the spirit and scope of the following claims.

We claim:

1. A core taker comprising: a core drill attachable to an operating string for receiving high pressure drilling fluid therefrom and having a central core-receiving passageway and a rearwardly-facing inside seat at the inner end of said passageway, said drill being adapted to have a core barrel insertable therein and removable therefrom through the operating string with the barrel, when in core-taking position, seating on said seat; means defining a fluid outlet in said drill separate from said passageway for discharging fluid from the interior to the exterior of said drill adjacent the cutting edges thereof; a resilient packing sleeve within said drill inwardly of said seat for snugly and slidably engaging the outer periphery of a core barrel seated on said seat for forming a fluid-tight seal between the barrel and said drill to prevent fluid flow between the barrel and said seat; and rigid means secured to said drill confining the end portions and outer side of said packing sleeve for positively retaining the latter in operative position within said drill.

2. The structure defined in claim 1 in which the rigid means comprises a tubular housing assembly secured at its forward end to the drill.

3. The structure delined in claim l in which the packing sleeve has an annular groove in each end thereof, said grooves being spaced inwardly of the outer edges of said ends, and the rigid means comprises a tubular housing having the forward end thereof threaded into said drill and a sleeve-retaining ring threaded into the other end of said housing against the corresponding end of said sleeve, said ring and housing having annular means interitting in said sleeve end grooves for retaining said sleeve in operative position.

4. In a hollow core drill attachable to an operating string for rotation thereby and reception of high pressure drilling uid therefrom and having a central core-receiving passageway, an inside seat for seating engagement of a Wire-line core barrel, and an outlet for drilling fluid separate from the passageway, the combination of resilient packing means within the drill in position to releasably receive and to snugly and slidably engage with the periphery of the core barrel when seated on the seat for sealing with the barrel and preventing flow of drilling uid between the barrel and the seat from the interior to the exterior of the drill via the core-receiving passageway; and rigid means secured within and to the drill and securely retaining said packing means in said position.

5. The structure defined in claim 4 in which the packing means comprises a sleeve of heat-resistant material.

6. A core taker comprising: a core drill attachable to an operating string for rotation thereby and reception of high pressure drilling fluid therefrom, said drill having a central core-receiving passageway and a rearwardly facing inside seat; a core barrel positionable within said drill to seat on said seat, said barrel being removable from and insertable in said drill through the operating string; means defining a fluid outlet in said drill separate from said passageway for discharging fluid from the interior to the exterior of said drill adjacent its cutting edges; resilient packing means positioned Within said drill to releasably receive and to snugly and slidably engage with the outer periphery of said barrel when seated on said seat for sealing with said barrel and preventing ow of uid between the latter and said seat from the interior to the exterior of said drill via said core-receiving passageway; and rigid means detachably secured within and to said drill and securely retaining said packing means in said barrel-receiving and engaging position.

7. In a core drill attachable to an operating string for rotation thereby and reception of high pressure drilling fluid therefrom and having a central core-receiving passageway, an outlet for drilling uid separate from the passageway, and a frusto-conical inside seat for seating engagement by a complementary end of a wire-line core barrel, the combination comprising: a rigid tubular housing detachably secured within and to the drill above and in alignment with the inside seat; and a resilient packing sleeve secured to and within said housing for reception of and for snugly and slidably releasably engaging a core barrel seated on the seat to form a fluid-tight seal between the barrel and the drill at a location between the fluid outlet and the core-receiving passageway, the inner diameter of said sleeve normally being only slightly less than the outer diameter of the core barrel to permit insertion and removal of the latter into and from said sleeve.

8. The structure dened in claim 7 in which both ends of the sleeve are provided with interior annular recesses, and the housing includes rigid axially-extending circumferential flanges engaged within said recesses to secure said sleeve within said housing.

References Cited in the file of this patent UNITED STATES PATENTS 1,489,797 Sutton Apr. 8, 1924 1,634,891 Trout July 5, 1927 2,068,762 Pennington Jan. 26, 1937 2,220,554 Straatman Nov. 5, 1940 2,234,264 Lang Mar. 1l, 1941 2,260,320 Hoioss Oct. 28, 1941 2,300,805 Pew Nov. 3, 1942 2,408,892 Stokes Oct. 8, 1946 FOREIGN PATENTS 397,743 Great Britain Dec. 2l, 1932 

